Paxton Lynch raised his right arm and pointed to the sky as he sprinted out of the Broncos’ tunnel between towers of smoke and fire. Sports Authority Field at Mile High shook as the sellout crowd stood on its feet to welcome the rookie Sunday afternoon. The stage and spotlight were his as he prepared for his first NFL start, against the Atlanta Falcons.

It was a moment Lynch had dreamt about for years, and worked toward the past six months since the Broncos drafted him in the first round as their quarterback of the future. But the cheers quickly quieted and the smoke and fire gave way to overcast skies as Atlanta handed Denver its first loss, 23-16.

The Broncos, seeking a 5-0 start, came undone behind the struggles of their young quarterback, shaky offensive line play and a porous run defense.

“We put him in a really tough situation,” coach Gary Kubiak said. “That’s not the type of game you want to put him in. We battled. Just didn’t play very good. You’ve got to give Atlanta a lot of credit. They came into our place, played with a lot of poise, made a lot of big plays and did a really great job once they got us down.”

Lynch finished 23-of-35 passing for 223 yards, one touchdown, an interception and an 81.0 passer rating. He also was sacked six times.

“I am upset, obviously, because we lost,” Lynch said. “I am kind of happy that I got the first one under my belt.”

Atlanta entered the game with the NFL’s most prolific offense and quickly put it on display, taking the opening kickoff and marching to a touchdown. The Falcons outgained the Broncos in yards 118-59 while jumping to a 10-0 first-quarter lead. Atlanta finished with 372 total yards, compared with Denver’s 267.

Denver’s defense held Falcons wide receiver Julio Jones, coming off a 300-yard performance a week earlier, to zero catches in the first half. But Atlanta’s running backs punched holes in the Broncos’ run defense, racking up 122 yards on 32 carries. Lanes were cleared, tackles were missed and the season-long weakness of Denver’s defense was exposed. The Falcons’ running backs also found gaping holes in Denver’s pass defense, accounting for 180 receiving yards.

“Very good job on their part,” Kubiak said. “They ran the ball extremely well. Their backs accounted for a lot of offense today.”

Joe Amon, The Denver Post

Vic Beasley (44) of the Atlanta Falcons strips Paxton Lynch during the third quarter. The Denver Broncos hosted the Atlanta Falcons on Sunday, Oct. 9, 2016.

And this time, Denver’s offense failed to respond as Lynch’s first start was peppered with signs of promise but marred by a bevy of miscues, missed throws and indecision. His first pass was a 14-yard completion to Emmanuel Sanders on the right sideline that converted a third-and-5 play. But the drive died after a pair of incompletions.

The Broncos’ second and third possessions offered more of the same: Completions, impressive scrambles and key conversions were scattered among overthrown passes, a sack and only a field goal to end a 10-play drive, making it 10-3.

Denver’s offensive line that was, again, without starting right tackle Donald Stephenson (calf injury), appeared out of sync — at best — as the Broncos’ running game managed only 84 yards on 24 carries.

Starting right tackle Ty Sambrailo, in his third game back from injuries, was often flattened by defenders and stepped over by his own backs before being benched in the fourth quarter.

“Ty’s played a ton of football for a guy that didn’t do much for eight weeks,” Kubiak said. “He got forced into that situation because of the injury to Donald and he’s held up well, in my opinion. Today was tough on a lot of guys.”

The roar of the crowd that stood on its feet as Lynch ran out of the tunnel before the opening kickoff quickly softened to a whisper as the Broncos were shut out in the first quarter and only mustered three points in the first half.

The start of the second half did little to reinvigorate the fans. The Broncos’ opening possession ended with a punt, and the second with an an interception that set up Matt Ryan’s 31-yard touchdown toss to running back Tevin Coleman, who sped past linebacker Brandon Marshall into the end zone.

The Falcons’ once manageable lead ballooned to 20-3. And their defense offered little opportunity for retaliation.

Atlanta’s defense had only four sacks before Sunday’s game, tied for the fewest in the league. Against the Broncos’ shaky offensive line and rookie quarterback, the Falcons produced six — with 3 1/2 courtesy of linebacker Vic Beasley.

“(Lynch) came to do his job, and up front we didn’t do well enough,” said Broncos offensive tackle Russell Okung. “Got to protect better, got to run the ball, got to take care of the little things in order to have success out there.”

Broncos safety T.J. Ward stripped the ball loose from Falcons wide receiver Michael Sanu at midfield to restore life in the stadium entering the fourth quarter, but Denver’s offense continued to stumble. Brandon McManus kicked a pair of field goals and wide receiver Demaryius Thomas caught a 3-yard touchdown pass in the waning seconds to make the score look respectable.

But the damage was done. The perfect record gone. The first start in Lynch’s NFL career behind him.

Next game: Thursday night at San Diego.

“If I get put in that situation again, I will know how to handle it a little bit better than I did the first time,” Lynch said. “I am glad I got the experience, but I am also upset that we didn’t come out with the win. I’m going to keep approaching it like I have been approaching it. I am going to take it day by day and if my number gets called again, I am going to make sure I am ready to play.”

Nicki Jhabvala is the lead Broncos and NFL beat writer for The Denver Post. She was previously the digital news editor for sports. Before arriving at The Post in 2014, she spent nearly two years as a senior staff editor at The New York Times and five years at Sports Illustrated.

Six seasons of fighting onto rosters and into starting roles caught the eye of the Broncos, who believe Case Keenum's mentality will be contagious in the locker room and his skill will stabilize an offense in disarray.